I'm in favor of experiments in maximizing the bandwidth on 2 meters. Amateurs can do 19.2 k sym/sec for data modes, so that would be a good choice for phone and image modes as well. Even with just 32QAM that would be 76.8 k bit/s, and get high quality speech vocoders without artifacts. Theoretically fitting in a 25 kHz channel, is what the FCC was probably desiring. Everyone seems to be using QAM with OFDM, and that would deprecate the use of carrier power with fractional modulation indexes on VHF.
Steve - Agreed. I think a lot of people would be shocked that such techniques CAN be used on VHF, not just microwave spectrum. I think narrowband is one of the specialities of Amateur Radio experimentation where we can exceed the technology of commercial users.
Was trying to get my head wrapped around say 8 OFDM carriers of 19.2 ksym/s using 32 QAM, which would be 614.4 kbit/s. I wonder how that would work mobile in Manhattan? 200 kHz BW would be like HD FM without the carrier. Alas, I have no VHF RF amp skills.
Thanks for posting about Raspberry Pi Connect. I agree with you that requiring to contact an authentication server with every connection has issues. But as somebody who had an article published in QEX about using a Raspberry Pi for operating a remote station, remote operating can get complicated, especially if you want to stream your radio's audio. Raspberry Pi Connect seems much simpler. Alas, Raspberry Pi Connect doesn't seem to be able to stream audio, or maybe I missed it. I have asked in a support forum if it can indeed stream audio. If not I'm hoping that feature might be on the product's roadmap.
Harry - I think the better technology to be paying attention to for your purposes is the 44Net VPN service that is still in development by ARDC (wish I had a pointer to send you, but "they're not talking about it" yet. THAT has the potential to set up a robust remote connection and then you can use all of the existing remote access techniques, including audio, in a secure way, including audio. My understanding (without having tested it) is that it will easily traverse all the IPv4 silliness, including CGNAT that we have to live with by big ISPs such as Starlink, which I use.
I'm currently using NoMachine which 1) encrypts traffic 2) opens up a hole in the router with uPnP and 3) has an interface with PulseAudio on the Raspberry Pi that requires a bash script to configure. But I'm all for a simpler approach, especially for streaming audio.
Another issue is that it appears that PipeWire is the future of streaming audio on Linux. NoMachine doesn't work with it and I fear that at some point PulseAudio will become deprecated.
I'm in favor of experiments in maximizing the bandwidth on 2 meters. Amateurs can do 19.2 k sym/sec for data modes, so that would be a good choice for phone and image modes as well. Even with just 32QAM that would be 76.8 k bit/s, and get high quality speech vocoders without artifacts. Theoretically fitting in a 25 kHz channel, is what the FCC was probably desiring. Everyone seems to be using QAM with OFDM, and that would deprecate the use of carrier power with fractional modulation indexes on VHF.
Steve - Agreed. I think a lot of people would be shocked that such techniques CAN be used on VHF, not just microwave spectrum. I think narrowband is one of the specialities of Amateur Radio experimentation where we can exceed the technology of commercial users.
Was trying to get my head wrapped around say 8 OFDM carriers of 19.2 ksym/s using 32 QAM, which would be 614.4 kbit/s. I wonder how that would work mobile in Manhattan? 200 kHz BW would be like HD FM without the carrier. Alas, I have no VHF RF amp skills.
Thanks for posting about Raspberry Pi Connect. I agree with you that requiring to contact an authentication server with every connection has issues. But as somebody who had an article published in QEX about using a Raspberry Pi for operating a remote station, remote operating can get complicated, especially if you want to stream your radio's audio. Raspberry Pi Connect seems much simpler. Alas, Raspberry Pi Connect doesn't seem to be able to stream audio, or maybe I missed it. I have asked in a support forum if it can indeed stream audio. If not I'm hoping that feature might be on the product's roadmap.
Harry - I think the better technology to be paying attention to for your purposes is the 44Net VPN service that is still in development by ARDC (wish I had a pointer to send you, but "they're not talking about it" yet. THAT has the potential to set up a robust remote connection and then you can use all of the existing remote access techniques, including audio, in a secure way, including audio. My understanding (without having tested it) is that it will easily traverse all the IPv4 silliness, including CGNAT that we have to live with by big ISPs such as Starlink, which I use.
Thanks. I'll have to keep an eye out for that.
I'm currently using NoMachine which 1) encrypts traffic 2) opens up a hole in the router with uPnP and 3) has an interface with PulseAudio on the Raspberry Pi that requires a bash script to configure. But I'm all for a simpler approach, especially for streaming audio.
Another issue is that it appears that PipeWire is the future of streaming audio on Linux. NoMachine doesn't work with it and I fear that at some point PulseAudio will become deprecated.